When an MVS scratch tape is added to an Object or Object Backup storage group, it is assigned the TAPEUNITNAME of the SETOAM statement that is associated with the storage group. Even though a tape unit name is specified for the group, the ACS routines (for ALLOC) can override this tape unit name specification by assigning the allocation to a Tape storage group that directs the allocation into an ATLDS or a MTL.

Example: The SETOAM statement can have a TAPEUNITNAME of 3480 associated with it. When the ACS routine runs for ALLOC, however, it overrides the information on the SETOAM statement and allocates the scratch tape to reside in an automated or manual tape library. In this case, the TAPEUNITNAME is automatically overwritten with the exact device type that was used to first mount the tape volume when it was first added to the storage group. The volume is allocated to a compatible tape device after it is ejected from the tape library dataserver.